Signaling system



E. R. TAYLOR Aug. 5, 1930.

SIGNAL'ING SYSTEM Filed Deo. 3l 1926 INVENTOR. u? @JW @GPQ ATTORNEY BY i /7 Y Patented Aug. 5, T930 UNITED STATES PATENT OFFICE EDMUND R. TAYLOR, 0F NEW YORK, N. Y., ASSIGN OR TO AMERICAN TELEPHONE AND .TELEGRAPH COMPANY, A CORPORATION OF NEW YORK SIGNALING SYSTEM Application filed necember'm, 1926. serial No. 158,317.

This invention relates to signaling systems, and particularly to arrangements for interconnecting a plurality of program sources to one or more program transmitting stations so that one or more program transmitting stations may transmit the program originating at any one of the program sources.

In systems for the transmission of programs originating at a plurality of program sources through a plurality of program transmitting stations, it is often the practice to route the circuits interconnecting the program sources and the transmitting stations through a centralpoint where any one of the program sources may be connected to any one or more of the transmitting stations.

In the'systems heretofore known, the program sources were disconnected from, and connected to, the appropriate transmitting stations manually. The manual operation of these circuits is considered inelicient and uneconomical because one or more men need constantly be available to make changes in the connections of the circuits, i. e., a program transmitting station must very often be switched from the circuit of one program source to the circuit of another program source. Thus, it becomes apparent that certain advantages would ensue if the control of the circuits between the various program sources-and the various transmitting stations could be placed entirely in the hands of the operator or operators at the transmitting staions.

In order to provide a system in which the operator at any one transmitting station may connect his transmitter to any one of a plurality of program sources, itis necessary that the operator at the transmitting station be able to connect the transmitting circuit which lies between his transmitting stationy and the centralJ switching point to any one of a plurality of circuits between thelcentral switching point and the corresponding program sources, in such a manner that the resultant overall circuit. will have a suitable transmission characteristic and so that the signal to 1 noise ratio will be satisfactory. .The operator must also be able to connect a second circuit known as an order circuit, i. e., a circuitv over Which supervisory signals maybe transmitted, which also lies between the transmitting station and the central switching point, to the circuit of any one of a plurality of program sources, which is not being used for the transmission of program matter.

Accordingly, it is one of the objects of this invention to provide a system for the connection of a transmittin station to a plurality of program sources, o ten referred to as pickup points, which shall be under the control Aof the operator at the transmitting station.

It will be apparent that to carry this object properly into eliect, the interconnected circuit must have a suitableI transmission characteristic as well as a satisfactory signal t0 noise ratio.

It is another object of this invention to provide a system for the interconnection of a transmitting station to which two circuits are associated, one for the transmission of program matter, and thevother for the transmission of supervisory signalshto a plurality of program sources, or pick-up'points, so that program matter coming from one of the program sources may be transmittedvover one of the circuits to the transmitting statien and so that supervisory signals from another of the program sourcesmay be transmitted to the same transmitting station over the other of the circuits. It is a further object to provide such a system in which these connections may be made lrapidly and accurately.

These latter objects may be accomplished by a suitable combination of machine switching apparatus, with various apparatus now in use for the supply of program Amatter coming from various studios over wirecircuits to various'broadcasting stationsyas will be shown and described in some detail hereinafter. While this invention will be pointed out with particularity in the appended claims, the

' At the central switching point there is ma- "capacity to nine program sources.

chine switching apparatus comprising selecting means for selectively connecting any one of the program sources to the transmitting station through a line ML and forselectively connecting another one of the program sources to the same transmitting station through another line MLK. Two selectors, one, the transmitting circuit selector, and the other, the order circuit selector, are shown in the drawing, each of which has five rotatable arms,`all located about the same shaft, so that as the shaft is rotated, the five rotatable arms revolve about the shaft in synchronism. One end of the shaft has a notched wheel '(not shown). Two Vrelays R1 and R1 control the rotation of the selector arms of the corresponding selectors. A ratchet arm (not shown) is associated with the armature of each of the relays, R1 and Rr', so that when the winding of either of these relays becomes energized, the corresponding ratchet arm moves across the notched wheel, the notched wheel not being rotated thereby. When the relay which was previousl energized becomes deenergized, a spring 'wiiich is attached to the armature of the relay moves the armature back to its normal position and the ratchet arm rotates the notched wheel in a clockwise direction, thereby advancing the position of each of the selector arms one step. It is well known in the art of machine switching, that all of the selector'arms move together, i. e., in Synchronism.

The selector arms SL1L to SLS, inclusive,'are associated with the main line ML1 and function to `selectively connect any one of the program sources to the transmitting station for the transmission of program matter therethrough. The selector arms SL( to SLS are associated with the main line ML1 and function to similarly connect one of {the program sources to the transmitting station for the transmission of supervisory or monitoring signals. Each selector shown is limited in Obviously, one hundred point selectors. or even larger selectors, could equally well be employed herein, and these selectors would accordingly increase the number of program sources controllable through the central switching point,

all of which is'within the scope ofthis invention.

' A dial Dl and a repeating coil T, are con-` of any well known type, preferably of the vacuum tube type, and an equalizer E1 which may preferably comprise inductance and capacity in shunt relationship and in series with resistance, are provided at the central switching point in connection with the transmission of program matter over the main line MLP A relay R2 is employed to close the filament circuit of theamplifier A when the amplifier is to be set into operation. Means may be included in the amplifier for controlling its gain to overcome the different attenuation magnitudes of the wire circuits, usually of different lengths, which lead to the various program sources. In the arrangement shown for the purpose of illustration, however, the gain of the amplifier A is preferably maintained constant and a simple distortionless artificial line AL1 and an equalizer E2 are suitably combined with the circuit of each program source so as to accomplish just what the gain controlling means would or- 1 dinarily accomplish, i. e., providethe same overall losses for the circuits of different program sources. The arrangement shown will cause no substantial change in the signal to noise ratio, inasmuch as bot-h the noise and i the signal are equally attenuated by the artificial line. The amplifier A may be considered to have a high impedance input circuit so that two or more of these amplifiers may be connected to the same program source i without appreciably affecting the transmission characteristic of the overall circuit. The artificial lines ALl, AL1 and AL, are terminated by the terminating resistances T. T and T, respectively. It will be understood,

however, that while each program source is shown connected to an. artificial line, an equalizer and a terminating resistance, only the terminating resistance is essential to the system, and either or both of the others, i. e., the artificial line and the equalizer, may be added thereto if conditions require it.

When supervisory, monitoring or like signals are to be transmitted from one of the program sources to the transmitting station, the line MLl is brought into operation and the signals are transmitted t-hereover. For the transmission of such signals, each equal-- izer, artificial line an-d transmitting resistance may preferably be removed fromy the connected circuit. Accordingly, relays R3, R3 and R5 are provided, one corresponding to each program source, each relay disconnecting the corresponding artificial line equalizer and terminating resistance When the supervisory,

monitoring, for like signals-are to be transvmitt'ed from the associated program source to the transmitting station...The relays R5, R5 and R3 are so arrangedthat when an assoclated program source is connected to a transmitting station for the transmission of supervisory signals, that programsource Will not be connected to a transmitting circuit selector,1but may be connected to one or morel other order circuit selectors. Yet when a particular program source is connected to a transmitting station for the transmission of program matter, these relays Will prevent the connection of that program source to an order circuit selector. Whenever a program source is connected -to the transmitting station through the order circuit selector, connection is made through repeating coils T1 and T2 and line ML Without the terminating resistance, the artificial line and the equalizer. Nevertheless, thiscircuit may also be employed for the transmission of program matter if the apparatus above mentioned is connected to the combined circuit at either the program source or at the transmitting station. Clearly, the addition of this equipment Will provide means for op erating the order circuit for the transmission of program matter during emergencies.

The dialing system presupposes that 0 be dialed before the number corresponding to one of theprogram sources is dialed. The current drains from the battery or batteries are very low except during'the process of dialing. If a great number of program sources Were to be connected to various transmitting stations in a large installation, it Would perhaps be desirable to employ a closed circuit dialing system, i. e., a system in which current Hows from the battery or batteries: only at times When a transmitting station is connected to a pick-up point. Such a system would eliminate the necessity of dialing-0 iirst and Wouldfgive a constant indica- 'tion at the transmitting station Whenever a selector Was in use. `Such a system can be provided by utilizing the principles of standard machine switching arrangements.

The operation of the system shown inthe drawing is as follows: The operator at the transmitting station pulls the dial D1' ol' normal by closing the contact b. Relay R4 then operates because of the flow of current from battery B1, the circuit including the battery B1, the Winding of relay R4, the main line M11, contacts c and b of the dial D1 and ground. Relay/R5,1preferably a slow-releasev relay, operates on the closure of the front contact of the armatu're of relay R4. The circuit ,to relay R5 .includes a battery B2, the winding .of the relay R5, the armature of 'fthe relay R,1 and ground. Inasmuch as the relay R5is a slow-release relay, it will ordinarily remain operated as long as the dial D1 remains otl' normal. Operation of the relay R5 causes the operation of relay R5, current flowing from battery B3 through the winding of relay R5', armature d of the relay R5 'and ground. As-the relay R5 operates, its armatures f and g are attracted, disconnecting the input of' the amplifier A. from the selector arms SL1 and SLZ. Closure of the contact of armature al of relay R5 puts ground on the selector arm SLS. Closure of the armature e of the relay R5 lconnects the'back contact of relay R1 to the Winding of the relay R1.

When contact b of the dial D1 starts to return to its normal position, the pulsing contact 0 of the dial D1 opens and closes periodically in avvell known manner. When the dial pulsing contact c opens, the Winding of the relay Rgbecornes deenergized, so that its armature becomes disconnected from the Windin of rel-ay R5 and becomes connected to the iront contact of armature e of the relay R5. Since the relay R5 is already operated, as noted above, ground is connected to the winding of the relay R1, causing the operation of the relay R1, the circuit of relay R1 including battery B1, the Winding of the relay R1, armature e ofthe relay R5, the armature of the relay R.1 and ground. When -the dial pulsing contact' c closes, the Winding of the relay R4 again becomes energized, attracting its armature and deenergizing the Winding of the relay R1. Accordingly, the selector arms SL1 to SL5, inclusive, are advanced one contact. Successive operations of the pulsing contact c of the dial D1 bring about further movements of the selector-arms SL1 to SL11, until these selector armsreach the 0 position. The ground on the selector arm SL5 furnished by closure of the armature 0l of the relay R5 then holds the relay R1 operated until the dial returns to its normal position, the circuit for the Winding of the relay R1 including battery B1, the winding of the relay R1, contact 0 and selector arm SLS, armature d of relay R5 and ground. After the dial has returned to its normal condition, the Winding of the relay R5 becomes deenergized. Thereafter, the Winding of relay R1 also becomes deenergized, advancing selector arms SL1 to SL5, inclusive, to position N. If, however, the selectorarms had originally rested on the position N and if, therefore, the number of pulses dialed was only suiicient to carry the selector arms to positionO on release of the relay R5, thel ground applied to the selector arm SLiWould also have caused the Winding of relay R1 to become energized by the flow of current from the battery B1 through the Winding of the relay R1. the armature of relay R1, the selector arm SL11 and ground. By opening this circuitv at the armature of relay Cal iso

Rl, relay R1 becomes deenergized, whereupon all of the selector arms SL, to SL3, inclusive, are moved to position N. lt will, accordingly, become apparent that in any case, aztter 0 has been dialed, the selector arms move a step further to position N so that the operator at the transmittin station may then dial a number correspon ing to any one of the program sources. When the number corresponding to one of the program sources is being dialed, the selector arms rotate in synchronism in the manner described hereinabove until finally, upon the release of the relay R3,

the selector arms move to the desired posi-v tion. When the selector arms reach the proper position, relay R6 releases, connecting the input of the amplifier A to the selector arms Sla, and SL2.

Ground on the selector arm SL, causes the filament circuit of the amplifier A to become closed by the flow of current Jfrom the battery B3 through the winding of relay R2, selector arm SL, conductor m and ground. lt is to be remembered that in the arrangement of this invention shown and described herein, the filament. circuit of the amplifier is closed only while program source is connected to a transmitting station. Relay R3 is operated because of the flow of current through its winding in the circuit which includes conductor m, armature h of the relay R3, the selector arm SL3, the armature of the relay R7, the winding of the relay R3, battery R3 and ground. As the relay R3 becomes energized, the back contact of relay R7 is short-circuited by the armature h of relay R3. rlhe program source connected to the leads S1 becomes connected through the armatures f and g of the relay R3 to the equalizer E2, the artificial line AL, and the termina-ting resistance T. These are connected with other points corresponding to that particular program source in multiple on the arcs traversed by the selector arms SL, and SL2 of the transmitting circuit selector. l/Vhen the relay R3 is not operated, the program source is then connected through the back contacts of relay R3 to the upper two arcs of the order circuit selector, the connections being made through the contacts ofthese arcs numbered 1. As pointed out above, the circuit to relay R3 passes through normally made contacts of relay R7 which is associated with the conductors going in multiple to the order circuit selector (only one of which is shown), so that Whenever the program source is connected to the order circuit selector, relay R7 is operated, and hence the program source can not be seized for connection to the transmitting circuit'selector. However, armaturehof relay R3 and its contact are in parallel with armature of relay R7 and its contact, whenever vrelay R3 is operated. Consequently, when relay R7 becomes operated, it can not release relay R3. Back contacts of maaier the relay R3 connect the program source to a number of order circuit selectors in multiple (only one of which is shown) so that Whencept that in the embodiment of the invention n shown herein, no filament circuit relay R2 is employed, and relay R7 is operated instead of relay R3.

Although only three program sources, often known as pick-up points, are shown herein, as many as nine program sources or pick-up points may be accommodated with the apparatus used, and as many more program sources or pick-up points may be accommodated as found desirable, with slight modification oi' the arrangement shown, within the scope of this invention. lt seems hardly necessary to repeat that the connections to the contacts on the upper two arcs having the selector arms SL, and SL2 and on the last arc having a selector arm SL5 are multipled to corresponding contacts on a number of other transmitting circuit selectors and that the contacts on the upper two arcs and on the last arc of the order circuit are similarly multipled to corresponding contacts on other order circuit selectors.

1While this invention has been shown in one particular embodiment merely for the purpose of illustration, it is to be understood that the general principles of this invention may be applied to other and widely varied organizations withoutdeparting from the spirit ot' the invention and the scope of the appended claims.

l/Vhat is claimedA is:

l. ln a signaling system, the combination of a plurality ot program sources each at a distant station, a transmission circuit at another station, a plurality of transmitting media, two extending from the transmission circuit to each program source, one trans-.

mitting medium transmitting program matter from each source to be transmitted by the transmission circuit, another transmitting medium transmitting supervisory signals between the transmission circuit and each program source, two selectorsl associated with each program source, means for transmitting coded signals from the transmission circuit to the various selectors so that only one of the selectors may become responsive to connect a corresponding program source to the transmission circuit through one transmitting medium for the transmission of supervisory signals, and means for transmitting coded signals from the transmission circuit to the various selectors so that another selector may becomeresponsive to connect another program source to the transmission circuit through the other transmitting medium so that the program of said source may be transmitted by said transmission circuit.

2. In a signaling station, a plurality of sources of program each at a distantstation, a transmission circuit to which a radio transmitter may be connected at another station, a control station, a plurality of transmitting media one interconnecting the station of each program source with the control station, two transmitting media interconnecting the transmission circuit with the control station,

two selective switching arrangements, means for transmitting a coded impulse from the transmission circuit to the control station over one of the transmitting media therebetween to render one of the selective switching arrangements responsive to connect the station of` a desired program source with the transmission circuit for the transmission of program matter, and means for' transmitting another coded impulse from the transmission circuit to the control room to render the other of the selective switching arrangements responsive to connect thestation of another program source with the transmission circuit for the transmission of supervisory signals.

3. In a. program selecting system, the combination of a transmission circuit, a plurality of program sources each located at a distant station, a plurality of relays one corresponding to each program source, each rela controlling the connection of the correspon ing program source to the transmission circuit, and means including apparatus for producing dialing impulses and apparatus responsive to said .impulses for selectively switching the transmission circuit from one of said program sources to any other of lsaid program sources Without the introduction of,

programl matter from vstill other of said sources, said means including arrangements for effectively operating the relay corresponding to any desired program source to the exclusion of the other of said relays.

4. In a program Aselecting system, the combination of af plurality of program" sources each located at a distant station, a control room, a transmission circuit which may be connected to a radio transmitter located at another station, said transmission circuit extending to the control room, a plurality of transmitting media each of which extends from one of the program sources to the control room, a plurality of relays one corre.

sponding to each programsource, each relay controlling the connection of the corresponding program source to the transmission clr'- cuit through the transmitting medium corresponding to the program source, selecting apparatus at the control room for selectively switching the transmission circuit from one program source to another without the introduction of program matter from still other of the program sources, said selecting ap- 

